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Mapping of the neutral hydrogen (HI) 21-cm intensity fluctuations across redshifts promises a novel and powerful probe of cosmology. The neutral hydrogen gas mass density, $\Omega_{\rm HI}$ and bias parameter, $b_{\rm HI}$ are key…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-10 Hamsa Padmanabhan , T. Roy Choudhury , Alexandre Refregier

The 21 cm emission from neutral hydrogen surveys holds great potential as a valuable method for exploring the large-scale structure of the Universe. In this paper, we forecast for the cross-correlation between the Thermal Sunyaev-Zel'dovich…

Cosmology and Nongalactic Astrophysics · Physics 2026-03-06 Ayodeji Ibitoye , Furen Deng , Yichao Li , Yin-Zhe Ma , Xuelei Chen

The first direct measurements of the HI intensity mapping power spectrum were recently made using the MeerKAT telescope. These measurements are on nonlinear scales, at redshifts 0.32 and 0.44. We develop a formalism for modelling…

Cosmology and Nongalactic Astrophysics · Physics 2024-04-17 Hamsa Padmanabhan , Roy Maartens , Obinna Umeh , Stefano Camera

Observations with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) have been used to measure the 21 cm intensity mapping auto power spectrum, at $z\sim 1$, over a frequency range from 608.2 MHz to 707.8 MHz at wavenumbers…

Intensity mapping (IM) of spectral lines has the potential to revolutionize cosmology by increasing the total number of observed modes by several orders of magnitude compared to the cosmic microwave background (CMB) anisotropies. In this…

Cosmology and Nongalactic Astrophysics · Physics 2020-12-22 Jurek B. Bauer , David J. E. Marsh , Renée Hložek , Hamsa Padmanabhan , Alex Laguë

Neutral hydrogen (H$_{\rm I}$) intensity mapping is capable of measuring redshift evolution of H$_{\rm I}$ density parameter $\Omega_{\rm H_{\rm I}}$, which is an important parameter to understand structure formation in the…

Cosmology and Nongalactic Astrophysics · Physics 2020-09-28 Shoichiro Tanaka , Shintaro Yoshiura , Kenji Kubota , Keitaro Takahashi , Atsushi J. Nishizawa , Naoshi Sugiyama

Using a spectral stacking technique, we measure the neutral hydrogen (HI) properties of a sample of galaxies at $z < 0.11$ across 35 pointings of the Westerbork Synthesis Radio Telescope (WSRT). The radio data contains 1,895 galaxies with…

The emission from neutral hydrogen (HI) clouds in the post-reionization era (z < 6), too faint to be individually detected, is present as a diffuse background in all low frequency radio observations below 1420 MHz. The angular and frequency…

Astrophysics · Physics 2009-10-29 Somnath Bharadwaj , Shiv K. Sethi , Tarun Deep Saini

We describe the scientific goals and survey design of the First Large Absorption Survey in HI (FLASH), a wide field survey for 21-cm line absorption in neutral atomic hydrogen (HI) at intermediate cosmological redshifts. FLASH will be…

We detect the neutral hydrogen (HI) radial brightness temperature profile in large-scale haloes by stacking 48,430 galaxies selected from the 2dFGRS catalogue onto a set of 21-cm intensity maps obtained with the Parkes radio telescope,…

Cosmology and Nongalactic Astrophysics · Physics 2020-10-14 Denis Tramonte , Yin-Zhe Ma

This paper introduces the Hidden Valley simulations, a set of trillion-particle N-body simulations in gigaparsec volumes aimed at intensity mapping science. We present details of the simulations and their convergence, then specialize to the…

Cosmology and Nongalactic Astrophysics · Physics 2019-11-19 Chirag Modi , Emanuele Castorina , Yu Feng , Martin White

HI intensity mapping is a new observational technique to survey the large-scale structure of matter using the 21 cm emission line of atomic hydrogen (HI). In this work, we simulate BINGO (BAO from Integrated Neutral Gas Observations) and…

Cosmology and Nongalactic Astrophysics · Physics 2017-11-22 L. C. Olivari , C. Dickinson , R. A. Battye , Y-Z. Ma , A. A. Costa , M. Remazeilles , S. Harper

This study investigates the estimation of the neutral hydrogen (HI) mass function (HIMF) using a Bayesian stacking approach with simulated data for the Five-hundred-meter Aperture Spherical radio Telescope (FAST) HI intensity mapping (HIIM)…

Cosmology and Nongalactic Astrophysics · Physics 2025-01-22 Jiaxin Wang , Yichao Li , Hengxing Pan , Furen Deng , Diyang Liu , Wenxiu Yang , Wenkai Hu , Yougang Wang , Xin Zhang , Xuelei Chen

Neutral hydrogen intensity mapping can in principle deliver rapid and large-volume cosmological surveys with exquisitely accurate redshifts that are determined directly from imaging. However, intensity maps suffer from very strong…

Cosmology and Nongalactic Astrophysics · Physics 2024-05-30 Rahul Kothari , Roy Maartens

Line intensity mapping provides a statistical approach to tracing the large-scale distribution of matter in the Universe. We apply the HI intensity mapping technique to interferometric data from the MeerKAT International GHz-Tiered…

The cross-correlation of optical galaxies with the neutral hydrogen (HI) radiation intensity can enhance the signal-to-noise ratio (SNR) of the HI intensity measurement. In this paper, we investigate the cross-correlation of the galaxy…

Cosmology and Nongalactic Astrophysics · Physics 2022-09-21 Furen Deng , Yan Gong , Yougang Wang , Shuting Dong , Ye Cao , Xuelei Chen

We present the results of a blind search for intervening HI 21 cm absorption toward 260 radio sources in the redshift range 0<z<2.74 with the Green Bank Telescope. The survey has the sensitivity to detect sub-damped Lyman-alpha (DLA)…

Astrophysics of Galaxies · Physics 2020-08-25 Kathryn Grasha , Jeremy Darling , Adam K. Leroy , Alberto D. Bolatto

Intensity mapping (IM) with neutral hydrogen is a promising avenue to probe the large scale structure of the Universe. In this paper, we demonstrate that using the 64-dish MeerKAT radio telescope as a connected interferometer, it is…

Cosmology and Nongalactic Astrophysics · Physics 2021-04-28 Sourabh Paul , Mario G. Santos , Junaid Townsend , Matt J. Jarvis , Natasha Maddox , Jordan D. Collier , Bradley S. Frank , Russ Taylor

Observations of the neutral Hydrogen (\HI ) 21-cm signal hold the potential of allowing us to map out the cosmological large scale structures (LSS) across the entire post-reionization era ($z \leq 6$). Several experiments are planned to map…

Cosmology and Nongalactic Astrophysics · Physics 2016-05-11 Debanjan Sarkar , Somnath Bharadwaj , Anathpindika S.

We explore the feasibility of HI galaxy redshift surveys with the Five-hundred-meter Aperture Spherical Telescope (FAST) and its proposed Core Array interferometry. Using semi-analytical simulations, we compare the performance of the FAST…

Cosmology and Nongalactic Astrophysics · Physics 2025-08-25 Zhenglong Li , Diyang Liu , Chengliang Xu , Yichao Li , Xin Zhang